This is an application for renewed support of an onging program of study on the physicochemical and biological properties of proteins and peptides in solution with emphasis on their interaction with each other and with small molecules. The following research is proposed: (1) fluorometric determination of the binding constants of the phenothiazine tranquilizers, chlorpromazine and trifluoperazine, and the control drug promethazine to mouse brain tubulin, and extension of these studies to psychoactive drugs from different classes of chemical compounds; (2) elucidation of the mechanisms whereby enkephalin and substance P inhibit the reassembly of tubulin into microtubules; (3) a CD study of the interaction of bradykinin and other peptide hormones with GM1-ganglioside and cerebroside sulfate; (4) continuation and extension of our CD and NMR studies on the solution conformation of bradykinin to alpha-aminoisobutyric acid-containing analogues and a 19F NMR study of the binding of (p-fluorophenylalanine8)-bradykinin to bovine uterine membranes; (5) completion of our CD and 13C NMR investigation of the solution conformation of the model peptide, trilysine; and (6) continuation and extension of our theoretical calculation on the mass transport of interacting macromolecules to include the antigen-antibody reaction, the isomerization of creatine kinase and the quantification of ligand-binding by counter ion electrophoresis.